1. Field of the Invention
The present invention relates to a solar cell module having a readable and writable memory medium, a solar cell module string comprising a plurality of solar cell modules and having a readable and writable memory medium, and a solar cell system having said solar cell module or said solar cell module string. The present invention also relates to a method of supervising said solar cell module or said solar cell module string.
2. Related Background Art
In recent years, societal consciousness of the problems relating to the environment and energy has been increasing all over the world. Particularly, heating of the earth because of the so-called greenhouse effect due to an increase of atmospheric CO.sub.2 has been predicted to cause a serious problem. In view of this, there is an increased demand for means of power generation capable of providing clean energy without causing CO.sub.2 build-up. In this regard, nuclear power generation has been considered advantageous in that it does not cause CO.sub.2 build-up. However, there are problems with nuclear power generation such that it unavoidably produces radioactive wastes which are harmful for living things, and there is a probability that leakage of injurious radioactive materials from the nuclear power generation system will occur when the system is damaged. Therefore, there is an increased societal demand for early realization of a power generation system capable of providing clean energy without causing CO.sub.2 build-up as in the case of thermal power generation and without causing radioactive wastes and radioactive materials as in the case of nuclear power generation.
There have been various proposals which are expected to meet such societal demand. Among those proposals, solar cells (i.e., photovoltaic elements) are expected to be a future power generation source since they supply electric power without causing those problems as above mentioned, and they are safe and can be readily handled. Particularly, public attention has been focused on a solar cell power generation system because it is a clean power generation system which generates electric power using sunlight. It is also evenly accessible at any place in the world and can attain relatively high power generation efficiency without requiring a complicated large installation. It can also be expected to comply with an increase in the demand for electric power in the future without causing environmental destruction. Various studies have been made in order to realize a desirable solar cell power generation system which is practical as a power supply source.
Incidentally, solar cells have been widely used since they are clean and non-exhaustible electric power sources. Various studies have been made in order to further improve them in terms of their performances. Besides, there have been proposed a variety of solar cell modules comprising a plurality of solar cells (or photovoltaic elements) sealed therein. For these solar cell modules, various studies also have been made in order to further improve them in terms of their performances. Some of these solar cell modules have been put to practical use, for instance, by installing them on the ground or a roof of a building.
In the case of installing a plurality of solar cell modules on a roof of a building, the execution work is usually conducted for every transportation or installation unit comprising a predetermined number of the solar cell modules. The solar cell module herein means a structural body formed by providing a plurality of solar cells, electrically connecting them to each other in series connection or parallel connection to obtain a solar cell array, and sealing said array into a panel-like shape. In the case of installing these solar cell modules on the roof, they are spacedly arranged on the roof at equal intervals, followed by electrically wiring them so that they are electrically connected with each other in series connection or parallel connection. The result of this process is generally called a solar cell module array.
Here, the term "array" is used in the case where both series connection(s) and parallel connection(s) are present. The term "string" is used in the case where only series connection(s) is present. In this respect, in the case of a structural body comprising a plurality of solar cells serialized with each other, the structural body will be hereinafter referred to as "solar cell string". Similarly, in the case of a structural body comprising a plurality of solar cell modules electrically serialized with each other, the structural body will be hereinafter referred to as "solar cell module string".
FIG. 16 is a schematic view illustrating an example of such solar cell module string installed on a roof of a building. As shown in FIG. 16, a plurality of solar cell modules 1602 are spacedly arranged on a roof 1601 of a building 1610. These solar cell modules 1602 each having a pair of positive and negative terminals (not shown) are electrically connected with each other in series connection by electrically connecting their positive and negative terminals by means of wiring cables 1603. The solar cell modules thus electrically serialized establish a solar cell module string. Reference numeral 1604 indicates a pair of cable terminal portions extending from the solar cell module string. The cable terminal portions 1604 are electrically connected to a connection box connected to an inverter (not shown) so that electric power generated by the solar cell module string is supplied into the inverter through the connection box.
In the above, because the electric power generated by the solar cell module string is of DC, the DC power is converted into an AC power by the inverter and then outputted.
The wiring cables 1603 are usually wired on the rear sides of the solar cell module in many cases in order to prevent them from becoming externally conspicuous.
In the configuration shown in FIG. 16, it is possible for the solar cell modules 1602 to be classified into several groups, each comprising a predetermined number of the solar cell modules which are electrically serialized with each other and having a pair of cable terminal portions. These module groups are separately connected to a connection box having a switching mechanism (not shown) and which is connected to an inverter through their cable terminal portions so that electric power generated by a given module group can be selectively supplied into the inverter through the connection box.
FIG. 17(a) is a schematic slant view illustrating a specific example of the configuration of each of the solar cell modules 1602 shown in FIG. 16, when obliquely viewed from the front side. FIG. 17(b) is a schematic cross-sectional view, taken along the line Y-Y' in FIG. 17(a). The solar cell module 1700 shown in FIGS. 17(a) and 17(b) is a roof-integral type solar cell module which also functions as a roofing material. Particularly, the solar cell module 1700 is suitable for use in batten seam roofing.
Description will be made of the structure of the solar cell module 1700 with reference to FIGS. 17(a) and 17(b). The solar cell module comprises a plurality of solar cells 1701 spacedly arranged on a flat face of a reinforcing plate 1740 whose opposite long edge side end portions are bent upward at 90.degree. on the light receiving face side, where the solar cells 1701 are electrically serialized with each other to establish a solar cell string. Each of the solar cells 1701 comprises a photovoltaic element group 1710 comprising a plurality of photovoltaic elements serialized with each other, where the photovoltaic element group 1710 is sealed by a surface covering material 1720 and a back face covering material 1730. Reference numeral 1750 indicates a terminal box which is provided at the rear face of the reinforcing plate 1740. A pair of power output terminals extending from the solar cell string are drawn through a hole (not shown) formed at a solar cell-free end portion of the reinforcing plate 1740 in the longitudinal direction and connected to the terminal box 1750. Reference numeral 1751 indicates a pair of cables extended from the terminal box 1750. The cables 1751 are electrically connected to the power output terminals from the solar cell string in the terminal box 1750. Each of the cables 1751 is provided with a one-touch system connector 1752. The roof-integral type solar cell module 1700 can electrically connect with another roof-integral type solar cell module (not shown) by connecting the connectors 1752 of the former with those (not shown) of the latter.
The roof-integral type solar cell module 1700 has the opposite long edge side end portions bent upward at 90.degree. in order to make the solar cell module suitable for use in batten seam roofing, where, if necessary, paint is applied to the solar cell module. In the case of practicing batten seam roofing, there are provided a predetermined number of roof-integral type solar cell modules having such configuration as shown in FIGS. 17(a) and 17(b). They are arranged on a roof of a building in accordance with the batten seam roofing method, and wiring is conducted to electrically connect them so as to comply with a predetermined electric design specification.
By the way, for solar cell modules having such configuration as above described which are manufactured in a factory, there is known a method of supervising them. In particular, a face plate having an inherent identification number is affixed onto a given position of each solar cell module, and when they are inspected and installed and when one or more of them are troubled and repaired, an administrative register or an administrative data base is prepared on the basis of the identification numbers of the face plates affixed on the solar cell modules.
This supervising method will be described in more detail while referring to the embodiment shown in FIG. 16, with reference to FIG. 18.
FIG. 18 is a schematic slant view illustrating one of the cell modules shown in FIG. 16, when such a face plate as above described is affixed onto a given position of the solar cell module. In FIG. 18, reference numeral 1602 indicates said solar cell module having a power generation region 1807 and frame 1805 having a face plate 1806 with an indication of an inherent identification number affixed onto its outer peripheral portion. The position for the face plate 1806 to be affixed is not limited to this. It is possible for the face plate 1806 to be affixed to an appropriate position of the rear face of the solar cell module 1802 or at an appropriate position of the surface of the solar cell module 1802 which is outside the power generation region 1807.
The face plate 1806 may comprise a metal plate or a soft member such as a seal or the like. Affixing the face plate 1806 as above-described may be accomplished with an appropriate fixing manner such as by means of an adhesive, vise, or the like.
As the indication means of the identification number, there can be mentioned, for example, a pattern with a printed serial number, a pattern with a bar-coded serial number, a pattern with a coded serial number, and the like. Besides, there can be mentioned such identification manners as described in Japanese registered utility model publication No. Sho.61-41261/1986 and Japanese patent publication No. Hei.5-38464/1993.
The foregoing information described in the face plate includes the type, rating, administrative number, or the like of a solar cell module. In the case where there is a large deal of information which cannot be entirely described in the face plate, it is possible to store information (particular management information) other than that described in the face plate for a given solar cell module in an information storage means, and when required, the information described in the face plate is verified with the particular management information stored in the information storage means.
The information storage means herein means an administrative register or an administrative data base comprising a computer or the like.
The particular information stored in the information storage means includes details of a given solar cell module such as the production date, the production place (factory), the production condition, the position to be installed, the constituents, the electrical performance, and the like. The information of the solar cell module such as the type, rating, administrative number and the like described in the face plate is sometimes stored in the information storage means such as the administrative data base.
The foregoing particular information also includes such information as described in the following. That is, for the solar cell module having been shipped as a product from a production factory and installed on a roof of a building, the information of collecting and recycling it is also included. Specifically, this information is meant to include information relating to maintenance, inspection, repair, recovery, removal and the like for the solar cell module installed on the roof.
In the case of obtaining necessary information for a given solar cell module from the administrative register or the administrative data base, a worker first obtains the information of the administrative number or the like described in the face plate affixed to the solar cell module. On the basis of the information obtained, the corresponding necessary information is selected from a large amount of particular information stored in the information storage means, and reference is made to the information thus selected.
It is possible to select a specific solar cell module from a plurality of solar cell modules by obtaining necessary information therefor from the information storage means and collating the information obtained with the information described in the face plates of the solar cell modules.
Now, in the case where a plurality of solar cells installed on a roof of a building are used over a long period of time, one or more of them are occasionally damaged with respect to their front surface by flying matter due to strong wind caused by a storm or the like. Such damaged solar cell module is occasionally desired to be replaced by a new solar cell module in view of security. In that case, prior to the replacement, the type, connector form and the like of the damaged solar cell module are ascertained on the basis of the administrative information described in the face plate affixed thereto. Then, a new solar cell module corresponding to the damaged solar cell module is provided, followed by replacing the damaged solar cell module by the new solar cell module.
In the case of obtaining the administrative information from the face plate affixed to the damaged solar cell module, a worker involved removes other solar cell modules situated around the damaged solar cell module. This method is problematic. Specifically, problems are encountered in the case where a number of solar cell modules, each having a face plate with such administrative information as above described which is affixed to the rear face or side face, are installed on the roof in accordance with the batten seam roofing method, one solar cell situated at a central position has been damaged, and the damaged solar cell module must be replaced. In order to obtain the administrative information described in the face plate affixed to the damaged solar cell module, the solar cell modules circumscribing the damaged solar cell module must be sequentially removed until the damaged solar cell module, and the administrative information described in the face plate affixed thereto, is ascertained. In this case, such problems as will be described in the following are entailed. The roof is kept in a partially demolished state until the type, connector form and the like of the damaged solar cell module are ascertained on the basis of the administrative information described in the face plate affixed thereto, a new solar cell module corresponding to the damaged solar cell module is provided, and the damaged solar cell module is replaced by the new solar cell module. In addition, after the roof is restored by replacing the damaged solar cell module by the new solar cell module, it is possible that ceratain defects could have been created, whereby rain may invade the roof structure.
Separately, such information as above described which is stored in the information storage means is intended to remain on each solar cell module. It is therefore necessary to provide a plurality of face plates at the solar cell module. But this is not practical. For instance, considering all the possible solar cell module scenarios when the solar cell module is inspected, a face plate containing information of its date and the result is affixed to the solar cell module; when the solar cell module is installed, a face plate containing information of its date, the installation place and the owner is affixed to the solar cell module, and when the solar cell module is troubled and repaired, a face plate containing information of the repair date, the troubled content and the repair result is affixed to the solar cell module. However, in this manner, it is necessary to affix an appropriate face plate to a given solar cell module for every action it undergoes. Accordingly, the number of face plates affixed to the solar cell module successively increases. Hence, this manner is complicated and difficult to efficiently practice. Thus, this method is impractical.
Incidentally, there have been proposed many techniques of disposing indication means contrived with respect to a character, designation, color or form at a light receiving face side of a solar cell module so that the solar cell module can be identified in accordance with an indication by the indication means.
These techniques are described, for instance, in the following documents.
Japanese registered utility model publication No. Sho.61-41261/1986 (hereinafter referred to as Document 1) discloses a solar cell (that is, a solar cell module) having a configuration in which a penetration pattern of a desired character, designation or the like is provided in the semiconductor layer forming the photoelectric conversion region. The penetration pattern is filled by an insulating material having a desired color, and said character, designation or the like is realized due to a difference between the color of the semiconductor layer and that of the insulating material.
Japanese patent publication No. Hei.5-38464/1993 (hereinafter referred to as Document 2) discloses a colored solar cell module which does not have a non-power generation region. Particularly, the solar cell module of Document 2 has a configuration in which a color filter and a color diffusing layer are disposed on the front face of a solar cell element. The color filter is capable of transmitting light having a wavelength matched to the power generation spectrum of the solar cell element, and the color diffusing layer comprises a light scattering layer capable of transmitting a part of the light transmitted by the color filter and scattering the residual light.
Japanese registered utility model publication No. Hei.6-27964/1994 (hereinafter referred to as Document 3) discloses a solar cell module having a configuration in which a solar cell element and a colored light scattering reflector are arranged in a mosaic state so that a desired character, designation or the like is realized by virtue of the colored light scattering reflector.
Japanese registered utility model publication No. Hei.7-26849/1995 (hereinafter referred to as Document 4) discloses a translucent thin film solar cell having a stacked body comprising a transparent electrode, an amorphous silicon layer and a metal layer formed on a translucent insulating substrate, wherein an identification pattern comprising said stacked body is provided at a portion other than the solar cell-forming portion.
Unexamined Japanese patent publication No. Hei.8-204220/1996 (hereinafter referred to as Document 5) discloses a solar cell module which has a power generation layer having an uneven surface provided with an irregular structure distribution such that the direction of incident light reflected varies depending on a position on the surface of the power generation layer to indicate an appropriate pattern.
Unexamined Japanese patent publication No. Hei.9-97918/1997 (hereinafter referred to as Document 6) discloses a solar cell module which has a surface covering material having a pattern indicating means for providing a display pattern of a desired character, designation or design on the light receiving face. The pattern indicating means comprises a patterned surface region capable of forming said display pattern and another patterned surface region having a surface pattern which is different from the former patterned surface region, and the two patterned surface regions are situated next to each other.
However, with respect to such identifying indication means used in solar cell modules as disclosed in the foregoing documents, there are disadvantages such that when certain indication information is installed, it is very difficult to change the information. It is also very difficult to delete the installed indication information and to install additional indication information in addition to the previously installed information.
In addition, there are also disadvantages such that the quantity of information which can be realized by the identifying indication means provided in the solar cell module is limited in view of the external appearance and also in view of an available space in the limited light receiving face. Therefore, the information which can be realized by the identifying indication means is eventually limited to a matter such as the type of the solar cell module, an inherent identification number corresponding to the production serial number of the solar cell module, or an administrative number for the solar cell module. In other words, the identifying indication means can retain only an information quantity to an extent which can be described in the foregoing face plate.
In this respect, for a number of solar cell modules which are installed on a roof of a building, when data (information), e.g., their types, administrative numbers, production dates, ratings, installation places, production condition, constituent materials (including their types, production plants, and administrative numbers), and the like, are stored in an administrative register or a database corresponding to the administrative register, in order to obtain necessary information for one of the solar cells with respect to their histories and the like for the maintenance work, it is necessary to retrieve the supervising register or the database based on the inherent identification number or the like of the solar cell module. Particularly, when information with respect to a specific solar cell module installed on the roof, e.g., inspection date or installation date, is required, it is necessary to refer to the administrative register in any case. In this case, when the solar cell modules installed on the roof are those provided with the foregoing identifying indication means on their light receiving face side, the specific ones can be more easily identified from the external appearance in comparison with the case of identifying a specific solar cell module, each provided with the foregoing face plate at the side face or rear face. This situation, wherein it is easy to locate the specific solar cell module, is not sufficient to efficiently and quickly conduct maintenance.
Specifically, the identifying indication means described in the foregoing documents have such disadvantages as will be described in the following.
Each of the identifying indication means described in Documents 1 and 3 is disposed in the light receiving face of the solar cell module, and it is such that other than the power generation region, the non-power generation region is provided, and a display pattern of a desired character, designation or the like is realized due to a difference between the color of the non-power generation region and that of the power generation region. Thus, there is a disadvantage such that when it is intended to increase the quantity of information to be indicated, it is necessary to increase the indication area for indicating said display pattern. Where the indication area is increased, the proportion of the indication area in the light receiving face is increased accordingly, resulting in a reduction in the power generation efficiency of the solar cell module as much as said proportion is increased.
The identification pattern as the identifying indication means in Document 4 comprises the stacked body which is substantially the same as the stacked body constituting the solar cell. This identification pattern is established by converting a part of a region capable of functioning as a power generation region into a non-power generation region by way of independent treatment by means of etching or the like. The identifying indication means described in Document 4 also has a disadvantage similar to that described in the above. That is, when it is intended to increase the quantity of information to be indicated, it is necessary to diminish the area of the power generation region in the limited area of the light receiving face. This situation results in a reduction in the power generation efficiency of the solar cell.
In order to form a desired character, designation or the like without establishing such non-power generation region as described in the above, it is considered that use of the configuration of the colored solar cell module described in Document 2 will be effective. In this case, there is an idea to modify the configuration of Document 2 such that the color filter (capable of transmitting light having a wavelength matched to the power generation spectrum of the solar cell element) and the color diffusing layer (comprising the light scattering layer capable of transmitting part of the light transmitted by the color filter and scattering the residual light) are disposed on the front face of the solar cell element. To that end, the color filter and color diffusing layer are shaped in a form corresponding to a desired character, designation or the like. This arrangement would form the character, designation or the like due to a difference between the color of the color filter and color diffusing layer and that of the solar cell element. However, in this case, a problem unavoidably occurs in that a remarkable reduction is caused in the power generation because a reflectance of about 30 to 50% and a transmittance of about 60 to 40% for incident light are required in order to offset the lowered power generation efficiency as described in Document 2.
In the case of the solar cell module described in Document 5, in which an appropriate pattern is indicated by varying the direction of incident light reflected depending on a position on the irregularly structured distribution-bearing surface of the power generation layer and also in the case of the solar cell module described in Document 6, in which a display pattern of a desired character, designation or the like is provided in the light receiving face by the two different patterned surface regions having a different pattern which are arranged next to each other in the light receiving face, it is possible to realize an appropriate display pattern while preventing the power generation from decreasing. However, in any case, it is required for the information (that is, the display pattern) to be indicated at such a magnitude that can be visualized. Therefore, there is a disadvantage such that it is difficult to store information at a high density, and therefore, the quantity of information which can be indicated is small.
The foregoing situations in the conventional solar cell modules in that the power generation is decreased in the case of increasing the quantity of information to be indicated and a large quantity of information is difficult to be indicated are also similar in the case of the conventional strings.